Lumbar Tap

Unfractionated Heparin, Therapeutic Dosing » recommended to discontinue unfractionated heparin (UFH) 2–4 h prior  to removal of spinal or epidural catheters to minimize risk of hematoma. » document normal partial thromboplastin time (PTT) prior to the procedure document a normal platelet count in patients who have » received heparin for 4 days or longer  because of the risk of heparin-induced thrombocytopenia (HIT). The half-life of heparin is 60–90 min. »

INTRODUCTION Major complications are extremely uncommon but can include: o cerebral herniation o injury to the spinal cord or nerve roots, hemorrhage (spinal hematoma), o infection Minor complications occur with greater frequency and can ! include: o Backache o post-LP headache o radicular pain or numbness !

Unfractionated Heparin, Prophylactic Dosing low-dose subcutaneous UFH of 5000 U subcutaneously subcutaneously » twice daily  unlikely to cause spinal hematoma Precautions to minimize risk include the following: » document a normal PTT prior to the LP document a normal platelet count in patients who have received heparin for 4 days or longer; perform the LP 1–2 h prior  to the next heparin dose, when the heparin effect should be minimal •

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Neuroimaging should be obtained in the ff conditions that can impose risk for potentially fatal cerebellar or tentorial herniation following LP: altered level of consciousness focal neurologic deficit new-onset seizure papilledema immunocompromised immunocompromised state Imaging studies should include the spine in patients with symptoms suggesting spinal cord compression, such as back pain, leg weakness, urinary retention, or incontinence In patients with suspected meningitis, administration of antibiotics, preferably following blood culture, should precede the neuroimaging study LP should NOT be performed through , as organisms can be introduced into the subarachnoid space (SAS) Coagulation defects including thrombocytopenia are at increased risk of , # permanent nerve injury and/or paralysis If bleeding disorder  is suspected, the platelet count , international normalized ratio (INR), and partial thromboplastin time  should be checked prior to LP Platelet count of 40,000/!L

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LMWH, Therapeutic Dose (e.g., Enoxaparin 1 mg/kg Subcutaneously q12h) » Patients receiving LMWH are at increased risk of postLP spinal or epidural hematoma . LMWH dose should be held for at least 24 h before  the » procedure

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Patient receiving antiplatelet or anticoagulant medications risk of bleeding complications Epidural space - the most common site of bleeding o Symptoms include: sensory or motor deficit and/ or » bowel/bladder dysfunction back pain occurs less commonly » o paraparesis #immediate surgical intervention, ideally within 8 h of onset of weakness, o minimize permanent disability #surgical intervention after 24 h is associated with a poor outcome

LMWH, Prophylactic Dose (e.g., Enoxaparin 1 mg/kg Subcutaneously q12h) Wait at least 10–12 h  after a prophylactic dose of » LMWH before inserting a spinal or epidural catheter to minimize the risk of spinal or epidural hematoma. !

Warfarin - spinal puncture is contraindicated during warfarin therapy Aspirin and Nonsteroidal Anti-inflammatory Drugs (NSAIDs) Use of these drugs does not appear  to be associated » with an added significant risk of spinal bleeding in patients having spinal or epidural anesthesia Reversal of drug effect on platelet function requires » stopping the drug for approximately 10 days for aspirin and for

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Ticlopidine/Clopidogrel Unknown effect » Discontinuing ticlopidine 14 days  prior to a spinal or » epidural procedure and discontinuing discontinuing clopidogrel 7 days prior to the procedure is recommended Abciximab, Eptifibatide, and Other Platelet Glycoprotein IIb/IIIa Inhibitors Platelet aggregation remains abnormal for 24–48 h » following discontinuation of abciximab and 4–8 h  following discontinuation of eptifibatide  Therefore, avoid LP until platelet is normal » 1

Direct Thrombin Inhibitors (e.g., Argatroban, Bivalirudin) Contraindicated » Oral Factor Xa inhibitor (Rivaroxaban) Contraindicated » Can cause epidural or spinal hematomas »

ANALGESIA Anxiety and pain  can be minimized prior to beginning the procedure. o Anxiety lorazepam, 1–2 mg given PO 30 min prior to the procedure or IV 5 min prior to the procedure ! Topical anesthesia can be achieved by the application of a lidocaine- based cream o Lidocaine 4% is effective when applied 30 min prior to the procedure o lidocaine/prilocaine requires 60–120 min o The cream should be applied in a thick layer so that it completely covers the skin; an occlusive dressing is used to keep the cream in place !

POSITIONING » Proper positioning of the patient is essential The procedure should be performed on a firm surface; » o If performed at the bedside # it should be edge of the bed and not in the middle The patient is asked to lie on his or her side, facing » away from the examiner, and to “roll up into a ball .” o neck is gently ante-flexed and the thighs pulled up toward the abdomen o the shoulders and pelvis should be vertically aligned without forward or backward tilt LP is therefore performed at or below the L3–L4 » interspace o spinal cord ends approximately at the L1 (94%) and L2–L3 interspace (6%) A line drawn between the posterior superior iliac crests, » which corresponds closely to the level of the L3–L4 interspace- useful anatomic guide Seated position - alternative to the lateral recumbent » position is the o patient sits at the side of the bed, with feet supported on a chair o patient is instructed to curl forward, trying to touch the nose to the umbilicus o It is important that the patient not simply lean forward onto a bedside tabletop, as this is not an optimal position for opening up the spinous processes o Can be helpful for px who are obese o Disadvantage: measurement of opening pressure is not accurate Bedside ultrasound  to guide needle placement may be » used in which LP is difficult using palpable spinal landmarks Computed tomography (CT)-guided needle placement » may be necessary in some more difficult cases

TECHNIQUE 1. Once the desired site for needle insertion has been identified, the examiner should put on sterile gloves . 2. A mask is worn to prevent droplet spread of oral flora during the procedure. 3. Clean the skin with povidone-iodine or similar disinfectant 4. Drape the area with sterile cloth 5. Blot the needle insertion site using sterile gauze pad to dry. 6. Local anesthetic, typically 1% lidocaine , 3–5 mL total, is injected into the subcutaneous tissue o pain associated with the injection of lidocaine can be minimized by slow, serial injections, each one progressively deeper than the last, over a period of ~5 min o Approximately 0.5–1 mL of lidocaine is injected at a time; the needle is not usually withdrawn between injections o A pause of ~15 s between injections helps to minimize the pain of the subsequent injection. o Approximately 5–10 mini-boluses are injected, using a total of ~5 mL of lidocaine o If possible, LP should be delayed for 10–15 min following the completion of the injection of anesthetic; this significantly decreases and can even eliminate pain from the procedure . Even a delay of 5 min will help to reduce pain. 7. LP needle (typically 20- to 22-gauge) is inserted in the midline, midway between two spinous processes, and slowly advanced. o bevel is maintained in a horizontal position, parallel to the direction of the dural fibers and with the flat portion of the bevel pointed upward; this minimizes injury to the fibers as the dura is penetrated o In sitting position, the bevel should be maintained in the vertical position o the needle is advanced 4–5 cm (1–2 in.) before the SAS is reached; the examiner usually recognizes entry as a sudden release of resistance, a “pop.” o If no fluid appears  despite apparently correct needle placement, then the needle may be rotated 90°–180 °. o If there is still no fluid , the stylet is reinserted and the needle is advanced slightly. o If the needle cannot be advanced  because it hits bone, if the patient experiences sharp radiating pain down one leg , or if no fluid appears (“dry tap”),  the needle is partially withdrawn and reinserted at a different angle. o If in the second attempt the needle still hits bone, then the needle should be completely withdrawn and the patient should be repositioned and needle can then be reinserted at the same level or at an adjacent one. 8. Once the SAS is reached, a manometer is attached to the needle and the opening pressure measured. o oscillations in CSF pressure associated with pulse and respirations should be noted ! upper limit of normal opening pressure with the patient supine is 180 mmH2O in 2

adults but may be as high as 200–250 mmH2O in obese  adults. 9. CSF is allowed to drip into collection tubes; it should not be withdrawn with a syringe and fluid is obtained for studies including: a. cell count with differential b. protein and glucose concentrations c. culture (bacterial, fungal, mycobacterial, viral) d. smears (e.g., Gram’s and acid-fast stained smears); e. antigen tests (e.g., latex agglutination); f. polymerase chain reaction (PCR) amplification of DNA or RNA of microorganisms (e.g., herpes simplex virus, enteroviruses g. antibody levels against microorganisms h. immunoelectrophoresis for determination of !globulin level and oligoclonal banding; i. cytology ! 15 mL of CSF is sufficient to obtain all of the listed studies 20–30 mL may be safely removed from adults ! ! A bloody tap due to penetration of a meningeal vessel (a “traumatic tap”) may result in confusion with subarachnoid hemorrhage (SAH) o CSF should be  immediately after it is obtained: ! clear supernatant #bloody tap ! xanthochromic supernatant # SAH o a bloody CSF due to the penetration of a meningeal vessel clears gradually in successive tubes, whereas blood due to SAH does not. 10. Prior to removing the LP needle, the stylet is reinserted to avoid the possibility of entrapment of a nerve root in the dura as the needle is being withdrawn; entrapment could result in a .

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the pain-sensitive dural sinuses, resulting in pain. o intracranial hypotension is the usual explanation for severe LP headache Treatment: usually resolves without specific treatment, care is largely supportive with oral analgesics  (acetaminophen, NSAIDs, opioids and antiemetics, and relief by lying recumbent or trendelenberg) o for some, beverage with caffeine can render temporary relief o For patients with persistent pain , treatment with IV caffeine (500 mg in 500 mL saline administered over 2 h) may be effective; atrial fibrillation is a rare side effect. o Epidural blood patch  accomplished by injection of 15 mL of autologous whole blood is usually effective; the injection is directed at the epidural space at the level of the initial LP ! has an immediate effect, making it unlikely that sealing off a dural hole with blood clot is its sole mechanism of action.

TABLE 443e1

Effective Strategies Use of small-diameter needle (22-gauge or smaller) Use of atraumatic needle (Sprotte and others) Replacement of stylet prior to removal of needle Insertion of needle with bevel oriented in a cephalad to caudad direction (when using standard needle) Ineffective Strategies Bed rest (up to 4 h) following LP Supplemental fluids Minimizing the volume of spinal fluid removed Immediate mobilization following LP  Abbreviation: LP,

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Considered as the principal complication of LP o 10–30% of patients Younger age and female gender are o associated with an increased risk of post-LP headache. Begins within 48 h but may be delayed for up to 12 days. Head pain is dramatically positional; it begins when the patient sits or stands upright; there is  upon  or with . The longer the patient is upright, the longer the latency before head pain subsides. The pain is usually a dull ache but may be throbbing; its location is occipitofrontal. Nausea and stiff neck often accompany headache, and occasionally, patients report blurred vision, photophobia, tinnitus, and vertigo. In more than 3/4 of patients, symptoms completely resolve within a week, but in a minority they can persist for weeks or even months. Etiology: caused by a drop in CSF pressure related to persistent leakage of CSF at the site where the needle entered the SAS. o  decreases the brain’s supportive cushion, so that when a patient is upright there is probably dilation and tension placed on the brain’s anchoring structures,

REDUCING THE INCIDENCE OF POSTLP HEADACHE

lumbar puncture.

Comparison of the standard (“cutting” or Quincke) lumbar puncture (LP) needle with the “atraumatic” (Sprotte). The “atraumatic” needle has its opening on the top surface of the needle, a design intended to reduce the chance of cutting dural fibers that, by protruding through the dura, could be responsible for subsequent cerebrospinal fluid leak and post-LP headache. FIGURE 443e2

(From SR Thomas et al: BMJ 321:986, 2 000.)

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TABLE 443e 2

CEREBROSPINAL FLUID CSF a 

Constituent

SI Units

Glucose

2.22–3.89 mmol/L

40–70 mg/dL

Lactate

1–2 mmol/L

10–20 mg/dL

Lumbar

0.15–0.5 g/L

15–50 mg/dL

Cisternal

0.15–0.25 g/L

15–25 mg/dL

Conventional Units

 Total protein

Ventricular

0.06–0.15 g/L

6–15 mg/dL

0.066–0.442 g/L

6.6–44.2 mg/dL

IgG

0.009–0.057 g/L

0.9–5.7 mg/dL

IgG indexb

0.29–0.59

Albumin

Oligoclonal bands (OGB)